An extremely large percentage of the world's vehicles run on gasoline using an internal combustion engine. The use of such vehicles, more specifically the use of vehicles which rely on fossil fuels (i.e., gasoline) creates two problems. First, due to the finite size and limited regional availability of such fuels, major price fluctuations and a generally upward pricing trend in the cost of gasoline are common, both of which can have a dramatic impact at the consumer level. Second, fossil fuel combustion is one of the primary sources of carbon dioxide, a greenhouse gas, and thus considered one of the leading contributors to global warming. Accordingly, considerable effort has been spent on finding alternative drive systems for use in both personal and commercial vehicles. Electric vehicles offer one of the most promising alternatives to vehicles that use internal combustion drive trains.
One of the main components relating to electric drive and energy storage is the battery. It is important to have accurate reporting of battery voltages and charge states. Misreporting can cause a loss in efficiency and overcharging. In some cases overcharging can even cause fire or explosion. Some systems may use redundant battery monitoring circuits to combat misreporting issues. If one circuit fails, there is a backup.